A form of pump and motor utilized in hydraulic power transmission comprises a rotor having a plurality of spaced radial vanes rotatable therewith and slidable relative thereto in slots provided in the rotor. The rotor and vanes cooperate with the internal contour of a cam to define one or more pumping chambers between the outer periphery of the rotor and the cam contour through which the vanes pass carrying fluid from an inlet port to an outlet port. Cheek plates are associated with each side of the cam and rotor through which the fluid flows to and from the rotating group. The passages and grooves in the cheek plates along with the cam contour define the pump cycles or zones, namely, fill (inlet), pre-compression transition (inlet to pressure), displacement (discharge) and decompression (discharge to inlet).
It has heretofore been recognized that it is essential for efficient operation of the pump to apply a biasing pressure to a chamber at the underside of the vanes in order to maintain them in contact with the cam. In the past pressure has been applied continuously or intermittently to the undersides of the vanes. In the continuous pressure arrangement, pressure is applied even when the vanes are in low pressure zones and has resulted in excessive cam and vane tip wear. In the intermittent pressure arrangement, pressure is applied to the vanes only when the vanes are in high pressure zones and only centrifugal force is utilized to urge the vanes toward the cam when the vanes are in low pressure zones.
It has heretofore been suggested and commercial devices have been made wherein additional pressure chambers are associated with each vane. The chamber at the base of each vane is commonly known as the under vane chamber and is subjected to cyclically changing pressure. The additional chambers are commonly known as the intra-vane chambers and are subjected to continuous high pressure. Typical devices are shown in U.S. Pat. Nos. 2,919,651, 2,967,488, 3,102,494, 3,103,893, 3,421,413, 3,447,477, 3,645,654, 3,752,609, 4,431,389 and 4,505,654. In such an arrangement, the contact of the vanes with the cam is controlled at all times by fluid pressure to the intra-vane and corresponding undervane chambers.
In such pressure energy translating devices, it is common to provide a shaft seal on the housing axially outwardly from the bearing that rotatably supports a shaft on which the rotor is mounted. When it is desired to replace the shaft seal, it is necessary to remove the pump from its installed position. This requires disconnecting the hydraulic lines and disconnecting the drive shaft.
Accordingly among the objectives of the present invention is to provide a hydraulic pressure energy translating device wherein the shaft seal may be readily removed and replaced; wherein the shaft seal can be pressurized even though the pump inlet is subjected to sub-atmospheric pressure and wherein in applications wherein the hydraulic fluid is a poor lubricant, the shaft bearing is protected from the hydraulic fluid.
In accordance with the invention, the hydraulic fluid pressure translating device comprises a cartridge including a cam ring including an internal contour, a rotor having a plurality vanes rotatable therewith and slidable relative thereto in slots in the rotor with one end of each vane engaging the internal contour. The cartridge includes a rotor and has an internal contour cooperating to define one or more pumping chambers between the periphery of the rotor and the cam contour through which the vanes pass carrying fluid from an inlet port to an outlet port. Two pressure chambers are formed for each vane and each vane has two surfaces one in each chamber, both being effective under pressure in the respective chambers to urge the vanes into engagement with the cam. The cartridge further includes support plates. One of the support plates supports an annular shaft seal that engages a shaft rotatably mounted in the housing and supporting the rotor such that when the cartridge is removed from the housing, the shaft seal is simultaneously removed. The housing further includes a simple pressure relief valve positioned to regulate pressure of the leakage prior to its passage to the pump inlet and the pressure acts upon the shaft seal to insure positive sealing regardless of the possible sub-atmospheric pressure at the pump inlet.